Abstract

A programme monitoring the prevalence of Salmonella infections in egg production farms with different types of flock management was conducted over a period of 18 months. Three laying hen farms with floor pens and five farms with batteries were examined from September 1992 to March 1994. A total of 569 samples (293 feed and 276 faeces) were processed in parallel by fivefold fractional enrichment in Rappaport/Vasiliadis medium and in potassium tetrathionate crystal violet broth. By using such elaborate methods, high detection rates of Salmonella were obtained. Two thirds of all isolates were found in the third to fifth selective enrichment procedure. Salmonella (S.) Tennessee was the most common serovar isolated (from 24.5% of the samples) whereas S. Enteritidis was the second most common isolate (23.7%). Salmonella were isolated from 33.1% of the feed samples (97/293), a result which may stimulate further discussion on the prevention of potential contamination of feed stuff with Salmonella and other pathogens. The number of Salmonella isolations from floor pens was significantly higher than from batteries. As time progressed an increase in the number of Salmonella isolations occurred in samples taken from the floor pens. The development of a less costly routine monitoring programme to detect Salmonella in samples taken from barns with layer flocks is recommended.